Citrate-induced impairment of neuromuscular transmission in human and experimental autoimmune myasthenia gravis

Two patients who underwent plasmapheresis for severe myasthenia gravis showed marked exacerbation of myasthenic weakness at the end of exchange sessions, in which citrate was used for anticoagulation. In one patient, improvement occurred after the administration of calcium but not after edrophonium. In rabbits and in rats with experimental autoimmune myasthenia gravis, decremental muscle response to 3 Hz repetitive nerve stimulation worsened significantly after injection of the citrate anticoagulant. The worsened neuromuscular transmission defect was reversed by the administration of calcium. When used for anticoagulation, citrate reduces serum ionized calcium levels and thus may aggravate myasthenic weakness and endanger patients during or immediately after plasmapheresis.     

Morphologic and immunologic studies in experimental autoimmune myasthenia gravis and myasthenia gravis.

An indirect immunoperoxidase technique was used to study by light microscopy the binding of serum from experimental autoimmune myasthenia gravis (EAMG) rabbits to junctionally and extrajunctionally located acetylcholine receptors (AChRs) in human and rat muscles. Binding was restricted to junctional AChR. Alpha bungarotoxin (a-BGT) partially blocked the binding of EAMG serum, while myasthenia gravis serum, carbamylcholine, decamethonium, and tubocurarine did not. A radioimmunoassay showed significant binding of antibodies in EAMG sera to 125l AChR. This binding was not inhibited by a-BGT, nor by carbamylcholine, decamethonium, or tubocurarine. Sera from 10 myasthenia gravis patients did not contain antibodies binding to the 125l AChR. We suggest that EAMG in rabbits induced by Torpedo AChR differs serologically from myasthenia gravis in patients, probably owing to antigenic differences between Torpedo and human AChR, and that antigenic differences also exist between junctional and extrajunctional receptors.     

Acetylcholine release in diaphragm of rats with chronic experimental autoimmune myasthenia gravis.

Recent evidence indicates that in chronic experimental autoimmune myasthenia gravis (EAMG) and in human myasthenia gravis, the defect of neuromuscular transmission results from immune-mediated destruction of post-synaptic membrane at the neuromuscular junction, with a reduction in the density of acetylcholine (ACh) receptors and decreased sensitivity to ACh released by nerve impulses. In the present study, the amount of ACh released by nerve impulse in rats with chronic EAMG and control rats of the same age, weight, and sex was compared. Phrenic nerve-hemidiaphragm preparations were stimulated in vitro, and the amount of ACh released was measured by bioassay. Despite a marked reduction in the amplitude of miniature end-plate potentials in chronic EAMG, ACh output at rest and during stimulation was not different from that of control rats. These data support the concept that the defect of neuromuscular transmission is due to a reduction of postsynaptic sensitivity to ACh.     

双类似物鼻黏膜耐受对实验性自身免疫性重症肌无力预防作用机制的研究

目的　观察双类似物 (Lys2 6 2 Ala2 0 7)对实验性自身免疫性重症肌无力 (EAMG)大鼠进行鼻黏膜耐受预防性给药后临床、免疫指标的变化并评价疗效 ,探讨鼻黏膜耐受对EAMG的预防作用机制。方法　建立Lewis大鼠EAMG模型 ,并在致敏前 10d(A组 ,10只 )及致敏当日 (B组 ,10只 )鼻腔给药 ,评价给药后A、B组及相应对照组CA组 (10只 )、CB组 (10只 )大鼠的临床症状并检测肌肉中乙酰胆碱受体 (AChR)含量 ,测定致敏第 4 2天血清抗AChR抗体IgG含量、第 5 0天淋巴结单个核细胞 (MNC)中针对AChR等特异性抗原的淋巴细胞增殖反应和CD4 + 及CD4 + CD2 5 + T细胞。结果　 (1)A、B组急性期和慢性期临床症状明显轻于相应对照组 ,A组慢性期临床症状轻于B组 ;(2 )A、B组慢性期血清抗AChR抗体IgG含量 [分别为 (2 2 0± 3 4 ) μg/ml和 (2 9 4± 4 6 ) μg/ml],明显低于相应对照组 [CA组 (4 2 6± 4 4 ) μg/ml、CB组 (4 3 2± 5 5 ) μg/ml],且A组低于B组 (均P <0 0 1) ;(3)A、B组大鼠肌肉AChR含量丢失明显低于相应对照组 (均P <0 0 1) ,且A组低于B组 (P <0 0 5 ) ;(4 )A、B组较各自对照组针对AChR等特异性抗原的淋巴细胞增殖反应均明显受抑 (均P <0 0 1) ;(5 )A、B组淋巴结中的CD4 + CD2 5 + T细胞含量均明显高于各     

预防性双类似物鼻粘膜耐受对EAMG的影响

目的选择双类似物(Lys262-Ala207)通过不同时间点对实验性自身免疫性重症肌无力(EAMG)模型进行鼻粘膜耐受预防性给药,观察其临床及免疫指标变化,并评价疗效,探讨预防性鼻粘膜耐受在EAMG中的预防作用机制。方法应用乙酰胆碱受体(AChR)加CFA致敏Lewis大鼠建立EAMG模型,并在致敏前10 d(预防耐受A组)及致敏当日(预防耐受B组)给予耐受肽Lvs262-Ala207及相应对照组CA、CB采用相同剂量对照肽MBP-p83-99鼻腔给药。检测给药后A、B组及相应对照组大鼠的体重、临床评分、肌电图、肌肉中AChR含量丢失变化及致敏第42 d血清抗AChR抗体IgG含量。结果急性期和慢性期A、B组体重明显超过相应对照组,临床症状明显轻于相应对照组,慢性期A组体重明显超过B组、病情明显轻于B组;A、B组低频重复电刺激出现衰减反应D5阳性率低于相应对照组;A、B组肌肉AChR含量丢失分别明显低于相应对照组,而A组低于B组;慢性期42 d A、B组IgG含量明显低于相应对照组,同时A组明显低于B组。结论本实验表明,预防耐受的疗效与自身免疫启动时间有关,启动前优于启动时耐受;双类似物鼻粘膜耐受预防不仅可有效地抑制临床症状,且可特异性减低致病性循环抗体含量和减少神经肌接头AChR含量丢失,为采用双类似物鼻粘膜耐受防治人类重症肌无力(MG)提供了依据。     

Influence of temperature on neuromuscular transmission in myasthenia gravis

Summary The effect of local cooling was studied in 28 patients with myastenia gravis. We stimulated the ulnar nerve with single stimuli and trains at 3/s for 2s and at 50/s for 1.5s. The compound muscle action potential (MAP), the muscle twitch and the isometric tetanic force of the adductor pollicis were registered. 1. At 3/s stimulation the pathological decrement of the MAP decreased after slight cooling. 2. The amplitude of the single MAP was higher at lower temperature when compared to normal temperature. The same increase is however to be found in healthy subjects. 3. After slight cooling, the maximum tetanic force was higher. However, the decrement of the force was higher also, therefore ruling out a practicable application of cooling for the patient. 4. After severe cooling (18–22°C) the tetanic force was much lower and in many cases a complete failure of the neuromuscular transmission occured.

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Zusammenfassung Der Einfluß lokaler Kühlung wurde an 28 Patienten mit Myasthenia gravis untersucht. Wir reizten den N. ulnaris mit einzelnen Impulsen und mit Serien von 3/s für 2s und von 50/s für 1.5s. Das Summenaktionspotential (MAP), die Muskelzuckung und die isometrische tetanische Kraft des Adduktor pollicis wurden registriert. 1. Bei Reizung mit 3/s war das pathologische Dekrement des MAP nach leichter Kühlung geringer. 2. Die Amplitude des MAP war größer. Diese Amplitudenzunahme tritt jedoch auch bei Gesunden nach Kühlung auf. 3. Nach leichter Kühlung war die maximale tetanische Kraft größer. Jedoch nahm die Kraft während der Reizung nach dem Maximum wieder schnell ab. Der praktische Nutzen einer Kühlung ist deshalb für den Patienten gering. 4. Nach starker Kühlung (18–22°C) war die maximale tetanische Kraft sehr niedrig. In vielen Fällen kam es zu einem vollständigen Versagen der neuromuskulären Impulsübertragung.

     

Lymphocyte responsiveness to acetylcholine receptor in rats with experimental autoimmune myasthenia gravis

We examined the time course of lymphocyte responsiveness to acetylcholine receptor (AChR) in rats with experimental autoimmune myasthenia gravis (EAMG). Rats were immunized with purified torpedo AChR. At intervals of one to eight weeks later, lymphocytes from the lymph nodes and spleen were cultured with purified torpedo AChR and rat muscle extract containing AChR. Lymphocyte responsiveness (stimulation index) was determined from uptake of ³H-labeled thymidine by the cultured cells. The response of lymphocytes to torpedo antigen began earlier and rose more rapidly than that to the homologous (rat) antigen. Lymph node cells responded more promptly than spleen lymphocytes. The stimulation indexes peaked at four to six weeks while antibodies to both antigens continued to rise. Delineation of this pattern of lymphocyte responsiveness sheds further light on the pathogenesis of the autoimmune response in EAMG and will be useful in the future design of immunotherapeutic strategies.     

Single-fiber electromyography in experimental autoimmune myasthenia gravis

The sensitivity of stimulated single-fiber electromyography in the detection of early abnormalities in neuromuscular transmission in experimental autoimmune myasthenia gravis (EAMG) was tested. Increased jitter and blocking were seen up to 3 weeks before clinical illness or decrement developed. Stimulation at 10 Hz appeared more sensitive in detection of abnormalities than stimulation at 3 or 5 Hz. Jitter values did not correlate with anti-Torpedo acetylcholine receptor (AChR), nor with anti-rat AChR antibody titer. No correlation was found between jitter and AChR loss or AChR-antibody complexes in muscle. It is concluded that, in addition to AChR loss and the presence of AChR-antibody complexes, other factors must determine the neuromuscular dysfunction in EAMG and possibly myasthenia gravis.     

Effects of sex hormones on experimental autoimmune myasthenia gravis.

To examine whether exacerbation of myasthenia gravis (MG) can be induced by changes in sex hormone levels we immunized 20 female Lewis rats with torpedo antigen to induce experimental autoimmune MG (EAMG). Ten of the animals underwent surgical ovariectomy prior to the induction of EAMG and 10 served as controls. Anti-acetylcholine receptor antibody (AChR-ab) titres and the degree of decrement on repetitive stimulation electromyography (REMG) at 3 Hz were obtained at base line and compared between rats with and without ovariectomy and a second control group of naïve rats. Three rats in each group were then injected with excess oestrogen and progesterone for one week, and three of the remaining rats in each group were given sham injections, and the degree of decrement on REMG and AchR-ab titres were re-evaluated. Immune reactivity of peripheral lymphocytes and splenic lymphocytes from all groups and controls was also determined. A comparable number of animals with and without ovariectomy developed clinical and electromyographic EAMG. The extent of decrement on REMG and AChR-ab titres did not change following hormonal replacement. Lymphocyte reactivity was similar for rats with and without ovariectomy. In conclusion, sex hormones do not appear to have an influence on the susceptibility to and the severity of MG.     

Disorders of neuromuscular transmission other than myasthenia gravis

Disorders of neuromuscular transmission in humans are caused by a wide variety of agents including systemic diseases, drugs, environmental toxins, animal envenomation, cations, and hormones. Some are genetically determined. Many are of known etiology. All such disorders interfere with one or more events in the sequence whereby a nerve impulse excites a muscle action potential. In many disorders of neuromuscular transmission, abnormal fatigue occurs, and some cases respond dramatically to treatment. Investigation of the microphysiology, microanatomy, and pharmacology of both normal and diseased neuromuscular junctions has increased our knowledge of these disorders.     

糖皮质激素受体阻断对大鼠实验性自身免疫性重症肌无力的影响

研究重症肌无力（ＭＧ）患者外周血白细胞糖皮质激素受体（ＧＲ）减少，而血浆皮质醇则在正常范围，探讨其与ＭＧ发病的关系。方法ＳＤ大鼠３２只，随机分成４组。实验组先以ＧＲ的竞争性拮抗剂米非司酮（ＲＵ３８４８６，ＲＵ４８６）阻断其ＧＲ，再以从人肌肉中粗提的乙酰胆碱受体（ｎＡＣｈＲ）进行免疫；实验对照组单用ｎＡＣｈＲ，试剂对照组只用ＲＵ４８６，而正常对照组仅用福氏佐剂。以临床症状、血清抗ｎＡＣｈＲ抗体（ｎＡＣｈＲ－ａｂ），重复刺激坐骨神经递减幅度为观察指标。结果实验组的临床症状和ｎＡＣｈＲ－ａｂ滴度升高及肌电图递减幅度均较明显，经ｔ检验分析，均与实验对照组有显著性差异（Ｐ＜０．０５），而试剂对照组和正常对照组均无ＭＧ的表现。结论ＧＲ被阻断后，对大鼠的实验性自身免疫性ＭＧ（ＥＡＭＧ）发病有易化作用。     

“Warming yang and invigorating qi” acupuncture alters acetylcholine receptor expression in the neuromuscular junction of rats with experimental autoimmune myasthenia gravis

Myasthenia gravis is an autoimmune disorder in which antibodies have been shown to form against the nicotinic acetylcholine nicotinic postsynaptic receptors located at the neuromuscular junction. “Warmingyang and invigoratingqi” acupuncture treatment has been shown to reduce serum inlfammatory cytokine expression and increase transforming growth factor beta expression in rats with experimental au-toimmune myasthenia gravis. However, few studies have addressed the effects of this type of acupuncture on the acetylcholine receptors at the neuromuscular junction. Here, we used confocal laser scanning microscopy to examine the area and density of immunoreactivity for an antibody to the nicotinic acetylcholine receptor at the neuromuscular junction in the phrenic nerve of rats with experimental autoimmune myasthenia gravis following “warmingyang and invigoratingqi” acupuncture therapy. Needles were inserted at acupressure pointsShou-sanli (LI10),Zusanli(ST36),Pishu (BL20), and Shenshu (BL23) once daily for 7 consecutive days. The treatment was repeated after 1 day of rest. We found that area and the integrated optical density of the immunoreactivity for the acetylcholine receptor at the neuromuscular junction of the phrenic nerve was signiifcantly increased following acupuncture treatment. This outcome of the acupuncture therapy was similar to that of the cholinesterase inhibitor pyridostigmine bromide. These ifndings suggest that “warmingyangand invigoratingqi” acu-puncture treatment increases acetylcholine receptor expression at the neuromuscular junction in a rat model of autoimmune myasthenia gravis.     

双类似物鼻粘膜耐受对实验性自身免疫性重症肌无力的影响

目的　在实验性自身免疫性重症肌无力 (EAMG)动物模型采用双类似物进行鼻粘膜免疫耐受 ,观察其临床及免疫功能变化 ,评价疗效并探讨其作用机制。方法　建立Lewis大鼠EAMG动物模型 ,选取经预实验证实有效的最低剂量为治疗量 ,检测致敏同时 (A组 )和缓解期第 1天 (B组 )给予双类似物鼻粘膜免疫耐受治疗后 ,大鼠体重、临床症状、致敏第 35天血清抗AChR抗体IgG含量及其淋巴细胞在不同刺激原作用下的增殖情况。结果　 (1 )治疗后EAMG大鼠体重增加 ,临床症状缓解。 (2 )治疗后血清抗AChR抗体IgG含量 (吸光度 ,A值 ) :A组 (0 98± 0 2 4 )和B组 (0 95± 0 2 6)均少于各自对照组 (分别为 1 1 8± 0 1 0和 1 1 9± 0 1 2 ) ,但A、B组间差异无显著意义。 (3)针对AChR等特异性抗原的淋巴细胞增殖指数 :A组 (1 71± 0 78)和B组 (1 97± 0 56)与对照组 (3 2 4± 1 31和 3 1 9±1 50 )相比均减低 ,增殖反应明显受抑制。结论　双类似物鼻粘膜耐受能明显缓解EAMG的肌无力症状 ,并伴有特异性T、B细胞免疫功能抑制     

Content and release of acetylcholinesterase in skeletal muscle of rats with experimental autoimmune myasthenia gravis

The effects of experimental autoimmune myasthenia gravis (EAMG) on acetylcholinesterase (AChE) were investigated in diaphragms of adult female Lewis rats. Both total AChE activity per muscle and release of enzyme activity during a 3-h incubation in vitro were measured. Two groups of myasthenic animals were used. Acute EAMG was induced by intravenous injection 48 h earlier with a syngeneic monoclonal autoantibody against the nicotinic acetylcholine receptor (AChR) of rat skeletal muscle; age- and weight-matched controls received a monoclonal anti-AChR antibody nonreactive with mammalian muscle. Chronic EAMG was induced by immunization 4 weeks earlier with AChR purified from Torpedo electroplax; controls received only adjuvants. When preparations from rats with acute or chronic EAMG were compared with the appropriate controls, no statistically significant differences in content or release of AChE activity were detected. Neither was there any change in the relative amounts of the various molecular forms of AChE in samples from animals with chronic EAMG. We conclude that the structural and functional changes arising in EAMG are highly specific for the acetylcholine receptor and associated elements of the neuromuscular junction, but have little impact on the biology of AChE.     

Response to gallamine: an indicator of diminished neuromuscular function in experimental autoimmune myasthenia gravis

A test for diminished neuromuscular function in animals with experimental autoimmune myasthenia gravis is described. Within minutes following an injection of gallamine triethiodide, mice exhibit a dramatic yet transient response which is dose-dependent. Mice previously inoculated with acetylcholine receptor are approximately twice as sensitive to gallamine as normal mice. Positive results have been found in over 80% of receptor-inoculated BALB/c mice and in 94% of C57Bl/6 mice.     

Effectiveness of Qiangjijianli capsule on experimental autoimmune myasthenia gravis

BACKGROUND: Experimental autoimmune myasthenia gravis (EAMG) and anti-AchR antibody of human myasthenia gravis are the same immune globulin. This antibody restricts the activity of nicotinic acetylcholine receptor and the amount of receptor binding sites is decreased, so myasthenia gravis occurs. OBJECTIVE: To observe the therapeutic effect and mechanism of action of Qiangjijianli capsule on EAMG rats. DESIGN: A randomized controlled animal experiment. SETTING: Experimental Animal Center of Guangzhou University of Traditional Chinese Medicine. MATERIALS: Acetylcholine receptors (AchR) were extracted from electric skate's electric organ which lives in the sea near Guangzhou. It had high biological activity and the protein content was 1.63 g/L. Qiangjijianli capsule (Astragalus mongholicus, Codonopsis pilosula, Atractylodes macrocephala, Angelica sinensis, Bupleurum chinense, Cairo morningglory root or leaf, Glycyrrhiza uralensis, etc. 0.5 g crude drug per capsule) was bought from the Manufacturing Laboratory of Guangzhou University of Traditional Chinese Medicine with the Batch No. 89-11-1. METHODS: This experiment was carried out in the Experimental Animal Center of Guangzhou University of Traditional Chinese Medicine from May to August 1990. ①Adult female SD rats were immunized with AchR. The animals' movement condition was observed and recorded everyday. Ten rats were chosen as normal control group, and they were not given any treatment and raised normally. After modeled, 20 successful rats were randomly assigned into 2 groups: treatmental group and model group. 2 mL Qiangjijianli capsule suspension (1 g) was intragastrically administrated into each rat of treatmental group for 30 days; The same amount of clean water was intragastrically administrated into the rats of model group for 30 days. ② Serum AchR antibody was measured with ABC-ELISA method. After administration, the rats were sacrificed. The complete diaphragmatic muscle was extracted for in vitro receptor binding test. The constitution of N-AchR per milligram of tissue was measured with FT-603 well-type γ scintillation detector and FH408 calibrater. ③ t test was used for the comparison of difference of mean value of two samples. MAIN OUTCOME MEASURES: The effect of Qiangjijianli capsule on the amount of binding site of serum AchR antibody and nicotine-like acetylcholinergic receptor（N-AChR）. RESULTS: Before Qiangjijianli capsule treatment, serum AchR antibody titre was close between model group and treatmental group (0.82±0.15 vs. 0.79±0.12, P > 0.05); After Qiangjijianli capsule treatment, serum AchR antibody titre of treatmental group was significantly decreased （0.45±0.11，t =6.602，P < 0.01）, and that in the treatmental group did not change significantly （0.71±0.13，P > 0.05）. So, serum AchR antibody titre of treatmental group was significantly lower than that of model group （t =5.780, P < 0.01）. ③ The number of N-AchR of normal control group was significantly more than that of model group [（1 503±156） mg·min－1 vs. (1 118±128) mg·min－1, t = 6.034，P < 0.01]. The number of N-AchR of treatmental group was significantly more than that of model group [(1 277±143) mg·min－1 vs. (1 118±128) mg·min－1, t =2.619，P < 0.05]. ③After the treatment of Qiangjijianli capsule, all of the six rats which had clinical symptoms in treatmental group did well more or less, while in model group, the six rats had no change except one. CONCLUSION: Qiangjijianli capsule can improve the symptoms of myasthenia gravis by immunological regulation and pharmacological effect of N-AchR.     

苏木醇提物治疗小鼠实验性重症肌无力的研究

目的观察苏木对重症肌无力的治疗效果。方法采用乙酰胆碱受体(AChR)加等量福氏佐剂多次免疫小鼠，复制实验性自身免疫性重症肌无力(EAMG)小鼠模型，将EAMG小鼠随机分为EAMG治疗组及EAMG对照组，治疗组胃内注入苏木醇提物，对照组给予等量生理盐水，治疗4周，观察治疗前后小鼠体重、游泳时间和临床评分变化。结果治疗前治疗组及EAMG对照组小鼠较佐剂对照组及正常对照组小鼠体重减轻、游泳时间缩短、临床评分增高，其差异具有显著性，但EAMG治疗组与EAMG对照组之间比较无显著性差异；治疗后EAMG治疗组症状明显改善，小鼠体重增加、游泳时间延长、临床评分降低，与EAMG对照组比较有显著性差异。结论苏木能明显缓解EAMG小鼠的肌无力症状，促进其功能恢复，是治疗重症肌无力的有效药物。